Multi-point toxic gas monitoring systems are available which use optically based technologies, including light emitting diodes (LEDs) to provide a beam of radiant energy for the sensing function. One form of gas analyzing cassette system is disclosed in U.S. Pat. No. 8,128,873 entitled, “Gas Analyzer Cassette System” which issued Mar. 6, 2012 and is assigned to the Assignee hereof. The '873 patent is incorporated herein by reference. Unfortunately, low yield and related production problems in connection with the light emitting diodes represent on-going challenges.
LEDs currently available in the market use GaP technology which provides very limited intensity (100 mcd), narrow viewing angle (20 degree) and a specific dominant wavelength 565 nm. The associated die materials exhibit unstable behavior causing LED intensity sudden drop and long term degradation, which can impact product performance and reliability.
One available solution to some of these problems is to change required wavelength so other higher intensity LED technologies (e.g. AlInGaP) can be used. Unfortunately, this approach requires significant efforts to reproduce and correlate gas concentration tables with actual gas tests. The typical test time is between six months to two years.